Seed endophytic bacterium induces a priming-like drought transcriptomic state in an invasive plant prior to stress...

Seedborne endophytes may facilitate plant establishment by modifying host responses to environmental stress, but the mechanisms underlying these effects remain poorly understood. This may be particularly important for invasive plants, whose establishment in novel habitats often depends on tolerance to abiotic stress.

Here, we examined whether the seed endophytic bacterium Erwinia tasmaniensis YJ6 induces priming-like drought-associated gene expression in the invasive plant Lactuca serriola. We compared the growth and root transcriptomes of uninfected and YJ6-infected plants grown under benign and drought conditions. YJ6 infection mitigated drought-induced reductions in shoot dry weight, root dry weight, and relative leaf growth, whereas these traits decreased in uninfected plants. Under benign water conditions, YJ6 infection induced 1,114 differentially expressed genes, including 317 genes that overlapped with drought-responsive genes in uninfected plants. Functional enrichment analyses showed that bacterial infection under benign conditions and drought exposure in uninfected plants affected several common pathways, including plant hormone signal transduction, phenylpropanoid biosynthesis, and nitrogen metabolism. YJ6 infection also affected genes associated with ABA-related signaling, gibberellin biosynthesis, and soluble sugar metabolism.

These results are consistent with the hypothesis that YJ6 infection may establish a priming-like transcriptomic state before drought exposure. This suggests a possible transcriptomic basis for seedborne microbe-mediated stress tolerance in invasive plants, although priming remains to be tested directly.